/**
* Computes the difference regions between this rectangle and {@code rect}. The
* return value is an array of 0 to 4 rectangles defining the remaining regions
* of this rectangle after the other has been subtracted.
* @param {goog.math.Rect} rect A Rectangle.
* @return {!Array.<!goog.math.Rect>} An array with 0 to 4 rectangles which
* together define the difference area of rectangle a minus rectangle b.
*/
goog.math.Rect.prototype.difference= function (rect){
return goog.math.Rect.difference(this, rect);
} ;